ფიზიკის სკოლა

Lazare Osmanov (2020-2024)
Publication: Eur. Phys. J. B (2022) 95:182 

Regular and Chaotic Motion of Two Bodies Swinging on a Rod

We investigate regular and chaotic dynamics of two bodies swinging on a rod, which differs from all the other mechanical analogies: depending on initial conditions, its oscillation could end very quickly and the reason is not a drag force or energy loss. We use various tools to analyze motion, such as Poincar´e section for quasi-periodic and chaotic cases. We calculate Lyapunov characteristic exponent by different methods including Finite Time Lyapunov Exponent analysis. Our calculations show that the maximal Lyapunov exponent is always positive except in the marginal cases when one observes quasi-periodic oscillations.

Publication: Eur. Phys. J. B (2022) 95:182 

George Gogaberishvili (2019-2023)
Publication: Monthly Notices of the Royal Astronomical Society, Vol. 503, 3592–3595 (2021)

Synchrotron emission from a nearby zone of Sgr A∗

Quasi-linear diffusion (QLD), driven by cyclotron instability, is proposed as a mechanism for the possible generation of synchrotron emission in the nearby zone of Sgr A∗. For physically reasonable parameters, QLD, by causing non-zero pitch angle scattering, lets electrons with relativistic factors of the order of 108 emit synchrotron radiation in the hard X-ray spectral band ∼120 keV.

Publication: Monthly Notices of the Royal Astronomical Society, Vol. 503, 3592–3595 (2021)

George Butbaia (2017-2021)
Publication: International Journal of Modern Physics D

In the Ellis wormhole metrics we study characteristics of fluid dynamics and the properties of linear sound waves. By implying the energy-momentum equation and the continuity equation in the general relativistic manner we examine the flow dynamics and solve the corresponding equations for a relatively simple case - radial flow. To study the linear sound waves the equations governing the mentioned physical system are linearized and solved and interesting characteristic properties are found."

Publication: International Journal of Modern Physics D

George Gogaberishvili (2019-2023)

Publication: International Journal of Scientific Research in Physics and Applied Sciences, 9, 5, (2021)

The effect of motion of the respiratory droplets on propagation of viral particles.

In this work we investigate viral load propagation due to liquid droplets expelled during respiratory actions.

We describe a mechanism of the transmission of such evaporating system and analyze dependence on several ambient parameters for different respiratory processes, such as sneezing, coughing and speaking. Our study has found that a significant amount of viral load and droplets from the respiratory fluid might transfer beyond the customary 2 m distance, understanding of which might give us a better insight about regulations and risks posed by an infected individual.

Publication: International Journal of Scientific Research in Physics and Applied Sciences, 9, 5, (2021)

George Bakhtadze (2015-2019)
Publication: International Journal of Modern Physics D

3D Study of centrifugal acceleration in isotropic photon field

In this paper we study relativistic dynamics of charged particles co-rotating with prescribed trajectories, having the shape of dipolar magnetic field lines. In particular, we consider the role of the drag force caused by the photon field the forming of equilibrium positions of the charged particles. Alongside a single particle approach we also study behaviour of ensemble of particles in the context of stable positions. As we have shown, together they create surfaces where particles are at stable equilibrium positions. In this paper we examine these shapes and study parameters they depend on. It has been found that under certain conditions there are two distinct surfaces with stable equilibrium positions.

Publication: International Journal of Modern Physics D, Vol. 26 (2017) 1750135

Centrifugal acceleration in the isotropic photon field

In this paper, we study centrifugal acceleration of particles moving along a prescribed rotating curved trajectories. We consider the physical system embedded in an isotropic photon field and study the influence of the photon drag force on the acceleration process.

For this purpose, we study three major configurations of the field lines: the straight line, the Archimedes’ spiral and the dipolar field line configuration. By analyzing dynamics of particles sliding along the field lines in the equatorial plane, we have found several interesting features of motion. In particular, it has been shown that for rectilinear field lines, the particles reach the light cylinder (area where the linear velocity of rotation exactly equals the speed of light) zone relatively slowly for bigger drag forces. Considering the Archimedes’ spiral, we have found that in cases when the field lines lag behind the rotation, the particles achieve the force-free regime of dynamics regardless of the drag force. Unlike this scenario, when the spiral is oriented in an opposite direction, the particles do not reach the force free regime, but tend to stable equilibrium locations.

Publication: International Journal of Modern Physics D

International Journal of Modern Physics D, Vol. 26 (2017) 1750135

Rati Goshadze (2014-2018)
Publication: Physics Letters A, Volume 383, Issue 10, p. 1027-1030

On the Filamentation Instability in Degenerate Relativistic Plasmas.

The filamentation instability of the electromagnetic (EM) beam in an underdense plasma with high level of degeneracy is examined by means of the momentum equation, continuity equation and Maxwell’s equations. It has been demonstrated that the instability develops for weakly as well as strongly relativistic degenerate plasma in and arbitrary strong amplitude of EM beams.

Publication: Physics Letters A, Volume 383, Issue 10, p. 1027-1030

Giorgi Tsereteli (2015-2019)
Publication: Physica Scripta, Volume 93, Issue 12, article id. 125601 (2018)

The role of second viscosity in the velocity shear-induced heating mechanism.
In the present paper we study the influence of second viscosity on non-modally induced heating mechanism. For this purpose we study the set of equations governing the hydrodynamic system. In particular, we consider the Navier Stokes equation, the continuity equation and the equation of state, linearise them and analyse in the context of non-modal instabilities. Unlike previous studies in the Navier Stokes equation we include the contribution of compressibility, thus the second viscosity. By analysing several typical cases we show that under certain conditions the second viscosity might significantly change efficiency of the mechanism of heating.

Physica Scripta, Volume 93, Issue 12, article id. 125601 (2018)

George Arsenadze (2015-2019)
Publication: International Journal of Modern Physics D Vol. 26 (2017) 1750153

Particles on the rotating channels in the wormhole metrics

In the Ellis–Bronnikov wormhole (WH) metrics, the motion of a particle along the curved rotating channels is studied. By taking into account a prescribed shape of a trajectory, we derive the reduced 1 + 1 metrics, obtain the corresponding Langrangian of a free particle and analytically and numerically solve the corresponding equations of motion.

We have shown that if the channels are twisted and lagged behind rotation, under certain conditions, beads might asymptotically reach infinity, leaving the WH, which is not possible for straight corotating trajectories. The analytical and numerical study is performed for two- and three-dimensional cases and initial conditions of particles are analyzed in the context of possibility of passing through the WH.

International Journal of Modern Physics D Vol. 26 (2017) 1750153

George Chanturia (2013-2017)
Publication: PHYSICS OF PLASMAS 24, 074501 (2017)

On the Raman instability in degenerate relativistic plasmas

The stimulated Raman scattering instability in a fully degenerate electron plasma is studied applying relativistic hydrodynamic and Maxwell equations. We demonstrated that the instability develops for weakly and strongly relativistic degenerate plasmas. It is shown that in the field of strong radiation, a degenerate relativistic plasma effectively responses as in the case of weak degeneracy.

PHYSICS OF PLASMAS 24, 074501 (2017)

Guram Mikaberidze (2011-2015)
Publications: Physics Letters A 379 (2015) 2730

Standing electromagnetic solitons in degenerate relativistic plasmas

The existence of standing high frequency electromagnetic (EM) solitons in a fully degenerate overdense electron plasma is studied applying relativistic hydrodynamics and Maxwell equations. The stable soliton solutions are found in both relativistic and nonrelativistic degenerate plasmas.

Physics Letters A 379 (2015) 2730

Irakli Gudavadze (2011-2015)
Publication: International Journal of Modern Physics D, Vol. 24, No. 6 (2015) 1550042 

On the role of rotation in the outflows of the Crab pulsar

In order to study constraints imposed on kinematics of the Crab pulsar’s jet, we consider motion of particles along co-rotating field lines in the magnetosphere of the Crab pulsar.

It is shown that particles following the co-rotating magnetic field lines may attain velocities close to observable values. In particular, we demonstrate that if the magnetic field lines are within the light cylinder (LC), the maximum value of the velocity component parallel to the rotation axis is limited by 0.5c. This result in the context of the X-ray observations performed by Chandra X-ray Observatory seems to be quite indicative and useful to estimate the density of field lines inside the jet. Considering the three-dimensional (3D) field lines crossing the LC, we found that for explaining the force-free regime of outflows the magnetic field lines must asymptotically tend to the Archimedes spiral configuration. It is also shown that the 3D case may explain the observed jet velocity for appropriately chosen parameters of magnetic field lines.

International Journal of Modern Physics D, Vol. 24, No. 6 (2015) 1550042